DUST
Presented by
Dianne Q. Robinson, PhD
Hampton University, Hampton, Virginia
What is
DUST?
“On Earth, dust forms when rocks are broken down into sand and
smaller particles. These particles, called mineral dust, can be blown
by the wind and suspended in the atmosphere.”
“ Desert dust contains common
crustal minerals, such as silica,
calcium carbonate, and iron oxides.”
“The deserts on Earth are huge sources of dust, with the
Sahara and Gobi Deserts as the main sources.
Desert dust is one of many types of tiny particles found in
our atmosphere called aerosols.”
African Dust Storms
This image shows dust
blowing from Baja
California.
Dust Storm
• A large body of small
airborne particles.
• Particles ranging from
small sand particles to
smoke to volcanic ash.
• Can travel thousands
of miles, crossing
continents and oceans,
affecting the entire
ecosystem of the
Earth.
Above:
A dust storm over Pakistan.
• Dust storms are a major part of our planet’s
ecosystem.
supply nutrient poor areas with nutrients from all
over the world.
balancing force in the world’s weather systems.
> cool the oceans and aid in cloud creation, as well
as reflect different wavelengths of light.
Clouds versus Dust Clouds
This diagram shows the difference in light
frequency reflection from clouds to dust.
Desertification
• Flux of African dust has increased dramatically since 1970
due to the ongoing drought in the Sahara and Sahel regions.
• The dust flux from Africa to the atmosphere has been
estimated in approximately 1 billion tons per year.
Desertification
The main causes of the spreading deserts in Africa are
climate, humans, and livestock.
Desertification vulnerability of Africa
Risk of human-induced desertification
Transportation of Dust
Transportation of Dust
• Wind picks up the dust and carries it up into
the atmosphere, up to 2 kilometers.
• This airborne dust can remain there for days,
depending on the size of the particles and the
strength of the wind propelling it.
Taklimakan Dust Storm
• A dust storm originating from China’s
Taklimakan Desert in May of 2007, traveled
around the world in just 13 days, depositing
dust into the Pacific Ocean just after it
completed its circuit.
• Enlarged image on next page…
Dust storm growing over the Taklimakan Desert.
Taklimakan Dust Storm
The cloud measured 3 kilometers
tall, 2000 kilometers long and was 8
to 10 kilometers above the surface
of the earth, it moved at about 36
kilometers per hour, and had a mass
of about 800 million kilograms.
A cold front over the desert created
strong surface winds which drove
the dust so high that the jet stream
caught it, and carried it around the
world.
Source Regions
• Most dust storms originate
in China and Africa.
• They carry dust across the
oceans, affecting major
weather systems, and local
ecosystems.
The orange area is
the Sahel Desert.
The Sahel is a good
example of a perfect
climate for dust.
The Sahel is the area
between the Sahara Desert
and the southern
grasslands.
The Sahel is responsible
for one-third of the
world’s dust production.
Years of drought and overuse of the soil have
depleted the aquifer, and
left the land vulnerable to
the wind.
Transportation of Dust
This diagram shows the
major global wind systems which carry dust.
African dust storm blowing towards the
Mediterranean Sea.
Dust Seasons
• China’s dust season runs primarily in the spring
(March - May).
• Africa’s dust seasons are complex in that the dust
never stops, only changes direction.
• Dust from Africa travels to the U.S. during the summer
in the northern hemisphere (May - November).
• African dust travels to Middle and South America
during the summer of the southern hemisphere
(December - April)
• Through both seasons, dust drifts up to Europe,
affecting their air quality.
Libyan dust blowing across the Atlantic Ocean.
The two tones of dust are two different material
compositions.
Dust from the Sahara Desert Reaches
Houston, Texas
United States
Aug 29 Aug 26
Aug 25
Aug 24
Aug 23
Aug 22
Aug 21
Aug 20
Aug 19
Africa
South America
NASA’s Terra Satellite Observations
From a Multi-angle Imaging SpectroRadiometer (MISR) instrument
Saharan Dust Composition
Components:
• Minerals (e.g. aluminosilicates, calcium
carbonate)
• Metals (Hg, Fe+3 )
• Radioactive isotopes ( e.g. Be-7, Pb-210,)
• Pesticides (e.g. DDT)
• Bioaerosols
Primary bioaerosols include:
• Pollen
• Fungi
• Bacteria
• Viruses
• Biological products (spores, mycotoxins,
endotoxins)
• Insects
• Fragmentary particles linked
to anthropogenic activities
such as agriculture
Impacts of Dust
• Dust could effect every
aspect of our climate,
from temperature, to
weather.
• Dust storms have
affected the topsoil
composition for a few
regions already.
• They can carry many
small particles, from
minerals to viruses.
A dust storm during the Dust
Bowl in the Midwest.
Impacts of Saharan Dust
Climate
Earth radiative budget
Cloud physical & radiative properties
Precipitation
Hurricane suppressant
Nutrient deposition
Ocean fertilization
Plankton productivity/algal blooms
Human Health
Respiratory
Cardiovascular
Other infections
Ecosystem Health
Aspergillosis (soft corals)
Plant pathogens
Detrimental Effects
> Dust could carry
viruses across the
world, making
containment and
quarantine nearly
impossible.
> There is a clear
link between dust
and asthma.
A dust storm in the Sahel, and a satellite picture
of that storm (top-right).
Detrimental Effects … continued
> Diseases can be carried by
dust to other parts of the
world.
> Coral reefs are a good
example of the disease
transportation.
> Caribbean Coral has been
one of the hardest hit coral
systems by dust borne
disease.
A coral formation with
Black Band Disease
Impacts of Saharan Dust:
Ecosystem Health
Saharan dust is an important source of fungal spores from species
that are not common in the Caribbean region.
We have been identified over 13 species of pathogenic species (i.e.
Aspergillus fumigatus, A. flavus, P. citrinum). Some are
environmental allergens and agents of asthma and infection.
Most of these species are considered opportunistic, primarily
affecting immunocompromised hosts.
Fusarium equiseti and Curvularia brachyspora are known plant
pathogens.
Aspergillus sydowii, responsible of Aspergillosis in soft corals, has
not been isolated from our samples.
ASPERGILLOSIS
 First reported in sea fans Gorgonia ventalina
and G. flabellum in mid 90s (Smith 1996).
 Dead tissue surrounded by purple halo that can
lead to death of colony.
 The pathogen has been described as
Aspergillus sydowii (Smith 1996).
 A. sydowii has been isolated from Saharan dust
samples.
 However other Aspergillus species (A. flavus)
has been found in necrotic tissue of sea fans (A.
Zuluaga, personal communication).
Aspergillosis
Healthy Gorgonia ventalina
• Aspergillosis is one of the most important diseases
affecting corals in the Caribbean Region.
Aspergillus sydowii
Coral Reef Bleaching
Photos courtesy of Hector Ruiz and Juan Torres
Beneficial Affects
> Dust storms cool the oceans, lessening the strength
of hurricanes by reflecting solar radiation back into
space.
> Dust storms carry nutrients all over the world to
stimulate ecosystems.
> African phosphorus carried by dust to the Amazon to
stimulate growth, thus helping to remove carbon
dioxide from the air.
African dust blowing across the Caribbean Sea
Satellites
CALIPSO
Earth Probe
Terra
Aqua
Satellite Evidence
A large cloud of dust being blown into the air
over Africa.
Satellite Evidence…continued
Dust from the Western Sahara being blown into the
atmosphere, then blown over to Central America,
losing strength as it passed over the Atlantic Ocean.
Images from Earth Probe satellite.
Satellite evidence…continued
Chinese Dust storm tracked across the Pacific
Ocean, landing in the U.S. and Canada in
April, 2001.
A RECENT NASA PUBLICATION:
“Understanding Earth: The Journey of Dust”